White Dwarfs May Aid Search For Habitable Planets, Alien Life

As the hunt for earth-like planets and alien life heats up, stars that are cooling down may be the best places to look. That's the word from researchers at Harvard and Tel Aviv University, who wrote about the promise of the dying stars -- white dwarfs -- in a new study.

"In the quest for extraterrestrial biological signatures, the first stars we study should be white dwarfs," Harvard astronomy professor Dr. Avi Loeb, who co-authored the study, said in a written statement.

What's so special about white dwarfs? They don't give off as much glare as bigger, hotter stars like our own Sun. That's important because planet-hunters often search for alien worlds by observing light from a star and checking to see if it dims at regular intervals -- a phenomenon that suggests the starlight is being blocked by an orbiting planet. An Earth-sized planet could block far more light from a white dwarf than from a Sun-sized star, so scientists wouldn't have to collect so much data to be confident that they'd found a new planet.

Once a planet was spotted orbiting around a white dwarf, the ultimate prize of detecting life-giving substances would be within reach. Oxygen would be "readily detectable" on such a planet, according to the study.

For now, however, the technology isn't ready. Co-author Dr. Dan Moaz, a professor of physics and astronomy at the University of Tel Aviv, told The Huffington Post in an email why the Hubble Space Telescope couldn't do the trick: "If this were almost the only thing Hubble would do, it would take about 5 years to accumulate the necessary signal. And, because it is in low-earth orbit, it can observe a given target only for some part of the year, so make that about 10 years. So, not practical!"

By contrast, they estimated that the James Webb Space Telescope, a Hubble successor that's slated to launch in 2018, would only have to observe intermittently for a few months to find oxygen on a planet orbiting a white dwarf.

So what would it be like to visit one of these worlds? For one thing, the years would be extremely short -- because the planet would be much closer to its star, an orbit would take only about ten hours as opposed to 365 days. In an email to The Huffington Post, Dr. Loeb added: "The sky on an Earth-like planet in the habitable zone around a white dwarf would look very similar to the sky on Earth... The color of a white dwarf that is a billion years old would also be the same as the color of the Sun, since it has the same surface temperature."

The study, "Detecting Bio-Markers In Habitable-Zone Earths Transiting White Dwarfs" is forthcoming in the Monthly Notices of the Royal Astronomical Society.